Automatic Call Distribution Systems (ACD) are well known for that reason are not described in detail. Such ACD is described generally in U.S. Pat. No. 4,788,718 and the references cited therein. Its basic function is to handle a number of callers greater in number than the number of available agents, at any one particular time. The ACD puts callers on hold and then, according to procedures designed into the system, connects the caller to the next available agent. Primitive systems use a simple queue where the first caller in is connected to the next available agent. Other systems use a pool of agents, some actively engaged in answering calls, others being held in reserve and being brought in when the number of callers on hold exceed a time dependent criteria. Each of these systems has as a disadvantage, an inability to control allocation of agents, by the population of callers at any one particular time. Previously, agent resources were allocated by entry order in a queue, or time in a queue, but not by population in the queue relative to active agents.
Further, the prior art was incapable of maintaining consistent intervals between announcements as the calling party was moved through various levels in the ACD. Announcements, usually given to notify the caller of its call status and reassure the caller on a periodic basis, depended upon the caller's call place in the ACD. As the call was shifted through the ACD, the announcement, coupled with each individual ACD level was played to that caller. However, as the periodicity of the announcement at each ACD level was unrelated to or dependent upon the periodicity for any other ACD level, a change occurring between announcements, altered the period between announcement occurring before and after such change. In this way, moving the call through various ACD levels disrupted the timing consistency in the message announcement interval, and the quality of reassurance to the called party, often times discouraging the called party from remaining on the line to wait for the next available agent.